This invention relates to an ignition timing control system for a marine propulsion unit and more particularly to an improved arrangement for controlling the engine operation in a marine propulsion unit.
As is well known, marine propulsion units normally include an outboard drive portion that is supported for trim adjustment on the transom of the associate watercraft so as to vary the trim angle of the propulsion device carried by the outboard drive. The propulsion device is driven by an internal combustion engine which may be mounted internally of the hull in applications employing inboard/outboard drives or which may be mounted directly upon the outboard drive in the case of outboard motors. With larger units of this type, it is frequently the practice to employ some form of powering device for achieving trim adjustment during running conditions. Frequently, the power device is comprised of an electric motor driven reversible pump that operates a hydraulic motor for achieving the trim adjustment. In some instances, the electric motor itself may also serve as the powering device through a mechanical connection between the electric motor and the outboard drive.
Regardless of whether an electrical, hydraulic or purely electrical power trim adjustment is employed, when the trim is operated, this places an additional load on the engine which can reduce its running speed. The simultaneous trim adjustment and reduction of engine speed and, accordingly, the speed of driving of the propulsion unit can deteriorate the handling and navigational capabilities of the watercraft for brief instances.
It is, therefore, an object of this invention to provide an arrangement for insuring that the speed of the powering engine will not be reduced when the power trim unit of a marine outboard drive is actuated.
It is a further object of this invention to provide an arrangement for insuring continuous running speed of the engine during power trim adjustment.
In many cases, such as marine outboard drive applications as previously described, the internal combustion engine in addition to powering a propulsion device, also powers other auxiliary components. When these components are caused to be operated, the added load on the engine can reduce its speed. Although arrangements have been incorporated for preventing such speed reductions, they tend to increase the speed of the engine under all conditions when the additional load is driven and regardless of whether engine speed increases are required.
It is, therefore, a still further object of this invention to provide an arrangement for controlling the speed of an engine which drives both a propulsion device and a load but which will effect only speed increases of the engine when the load is operated and the engine otherwise requires the speed increase.